Once you download a package to your local database from an unsynced/bad mirror, just switching mirrors won't remove that package from your local database, you need to force a database sync
sudo pacman -Syy. That is why it is so vital to always run
mirror-check prior to updating, or use
upd for your updates.
But I will check linux-firmware in [core], see if it is needed to redo the database for that package.
I checked the db, linux-firmware has a wrong db entry, will redo shortly.
I ended up rebuilding linux-firmware, database creation kept showing a bsdtar error for adding the linux-firmware package. Once your mirrors are synced linux-firmware 20190628-2 should install cleanly.